Transparent Energy Usage

Viewing Energy Usage in the HMI. See what Our Experts Have to Say

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When we talk to customers about controls upgrades, we're starting to get questions about viewing energy usage in the HMI, and sometimes sending energy consumption data to asset management systems. This is mostly about electric motors, but there's a little air consumption involved, too. We make modular equipment that lets users plug in various modules to their line for product flexibility, so some of them are looking for the more energy-efficient scheduling. What can you tell me about how this can be included in open-standard-based automation?

—From January '11 Control Design

Answers

Easing Data Collection

Viewing energy consumption is a critical first step toward reducing usage and cutting production costs, so it's no surprise that many end users across all industries look for quick and easy access to their consumption data. The good news is that existing automation infrastructures can help end users access and leverage that information seamlessly.

Most machine designs include the necessary meters and sensors to gather that energy usage data for regulatory compliance or batch management. But by pulling that information into energy historian software, users can track historical consumption data, monitor real-time usage and build role-based dashboards tailored to display information specific to performance goals.

For example, executives can view high-level KPIs, including total energy costs per plant compared to production output and greenhouse gas emission alerts that are color-coded based on pre-determined baselines. Meanwhile, plant and facility managers can separate energy consumed by the facility itself vs. energy consumed by production assets and can view individual consumption and emissions reports for any line or individual machine in the plant. They can determine the most efficient lines to run, based not only on operating efficiency but on overall costs as well.

Similarly, machine operators can view energy costs per hour compared with other shifts on the same line to promote and reinforce behavioral changes, while maintenance personnel can view fluctuations in the energy signature of individual assets to proactively identify potential problems.

Cliff Whitehead, Manager, Business Development,
Rockwell Automation, www.rockwellautomation.com

Integrated Power Measurement

The largest consumer of energy in most control systems is typically the drives and motors. Today, suppliers offer integrated power measurement capabilities directly in their servo drives, variable-frequency drives (VFDs) and even stepper controllers. In addition to providing current and voltage, these drives offer information on real power, reactive power and apparent power. Drives with active power supplies can regenerate power back onto the main line instead of wasting it in braking resistors. This is done, for example, when decelerating a large inertia. These drives can then provide information on the consumed and regenerated energy as well as the energy balance over time.

Another way to monitor power consumption is with power measurement I/O modules. These modules attach to a PLC much like standard I/O, but have specific capabilities for measuring the three-phase or single-phase power of a system. These I/O modules round out the energy measurement product offering by allowing machine builders and end users to measure energy consumption of non-motion components as well as devices outside the control system, such as furnaces. These modules also can measure the power consumption of drives from manufacturers that don't have this feature built in.

Because these power measurement I/O modules can be used on most common fieldbuses, they can be added easily to any brand of PLC or even retrofitted to machines in the field. Some energy-conscious users have even installed plant-wide energy measurement systems that use these modules on each one of their systems. This is a relatively low-cost solution to monitor production energy, and can be tailored to fit most existing facilities.
All this energy consumption data is readily available to the PLC and can be monitored and trended easily on the HMI. Programmers can work with these values in whichever IEC 61131 language they prefer. The information can be used to generate energy usage reports, calculate operating costs, and create best operating practices. The information can also be shared over OPC, web server, or any standard Ethernet protocol to an asset management or ERP system.

Nathan Massey, Regional Sales Manager,
B&R Industrial Automation, www.br-automation.com

Different Perspectives

This question has three parts:

Can we get data about energy usage to the HMI? There are a wide variety of helpful software options to cost-effectively get energy usage data to your HMI. Today's emerging standard for this is OPC UA, which is a secured method of transporting data from the PLC up to an HMI or across the web to anywhere in the world. If you are looking for direct access or gateway-based access, HMI platforms like those from Indusoft or gateway software from Kepware can operate with Beckhoff controls natively, permitting simplified communications setup via software wizards.

How can we send this information up to management level systems? Again, there are many ways to tackle this, but one way is to use the TwinCat Database supplement. This software package allows the PLC developer to establish communication with an array of databases (SQL, MySQL, Postgress, Access, etc.), both locally on the same PLC or across the network. The configuration for this can be set up using the database wizard and, depending on the requirements, can be done without writing additional code. For more complex implementations, you can perform Insert and Select statements to add data on-demand from the program. Obviously, this provides benefits to the machine builder because it eliminates many layers of communication between the database tool and the PLC, in turn decreasing development time and simplifying supportability in the long run.

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